A smart card, also known as an IC-card or a chip card, is a flat normally plastic card that may be as large as a credit card or, in particularly when used as an SIM (subscriber identity module), as small as a postage stamp. Such a card carries active and passive circuit elements. When used, for instance, as a SIM card it has a small processor and enough memory to hold data regarding the identity and preferences of a user. Such a SIM card is commonly used in a cellular telephone to allow a user to transfer his or her phone book and other data from one phone to another.
The card reader must fulfill several functions in addition to the obvious one of forming connections between contact points on the card and traces of the printed-circuit board normally carrying the holder. First of all it must hold and protect the card physically, something that is particularly important as, for instance, in a cell phone the card holder is in the bottom of the battery compartment where it is exposed as batteries are changed. In addition the card holder must shield the card, in particular from inductive and RF (radio-frequency) fields, another problem particularly present in a cell phone where the card is located a few centimeters from a transmitter.
In commonly owned U.S. Pat. No. 6,863,537 such a holder is described that has a dielectric base fixed to a grounded support and formed with a throughgoing cutout and a conductive cover forming a slot dimensioned to hold a smart card and pivotal on the base between an open position partially raised from the base and a closed position closely juxtaposed with the base and covering the cutout. Ground contacts carried on and electrically connected to the cover are positioned to engage through the cutout directly with the base in the closed position of the cover. Similar holders are described in U.S. Pat. Nos. 5,226,826 and 5,996,891.
Thus with this system closing the cover automatically establishes a connection directly with ground when it is closed, not via any intermediaries. The connection is direct, especially when according to the invention the ground contacts are of the same material as the cover, in fact unitary with the cover. Normally the ground contacts are formed as spring fingers. Thus these ground contacts can be provided without appreciably increasing the production costs of the card holder.
Nowadays the standard SIM card, which normally measures 15 mm by 25 mm is being replaced by a smaller so-called USIM card measuring a mere 12 mm by 15 mm, as the standard application for such a card is in a cellular telephone and these devices are getting ever smaller. Such a card is somewhat more difficult to handle. Getting it into and out of the slot in the holder cover is difficult. In addition the holder for such a small card must be dimensioned also as small as possible.